Amine storage, metabolism, uptake, and release are examined in platelets with a variety of techniques including radiolabelled tracers, nuclear-magnetic resonance and microanalytical electron microscopy. The studies have four principal objectives: (1) to delineate the factors controlling the intracellular disposition of serotonin and other biogenic amines; (2) to evaluate the role of psychoactive drugs, genetically-linked disorders, physiologic aging, and species differences on the dynamics of platelet function; (3) to correlate predictive factors such as monoamine oxidase activity in human-platelet sonicates with the in vitro function of intact platelets; (4) to use the concepts and techniques developed in connection with the study of platelets to evaluate structure-function relationships in synaptosomes.